Background Special day-care centres for atopic children have been established in Sweden.

Objective To study concentrations of cat (Fel d 1) and dog (Can f 1) allergens in settled dust and airborne cat allergen in day-care centres in relation to pet ownership among children and staff, ventilation and general cleaning.

Methods Twelve allergen avoidance day-care centres and 22 conventional day-care centres were included in the study.

Settled dust was collected and analysed with ELISA.

Airborne cat allergen levels were measured in eight allergen avoidance and seven conventional centres with a personal air sampler and analysed with an amplified ELISA.

Air change rate per hour (ACH) was measured.

A questionnaire which focused on keeping of cat and dog among staff and children and frequency of general cleaning was used.

Results In the allergen avoidance day-care centres neither children nor staff reported ownership of cats or dogs, compared with 21/22 of the conventional centres in which children and staff kept furred animals.

Fel d I and Can f 1 were found in settled dust in all day-care centres.